This invention relates to a method for the manufacture of dihydric phenols in high yields by oxidizing monohydric phenols represented by the generic formula: ##SPC1##
(wherein, R is one member selected from the group consisting of H and alkyls having 1 - 12 carbon atoms) and phenyl ethers represented by the generic formula: ##SPC2##
(wherein, R" is one member selected from the group consisting of alkyls and aryls having 1 - 12 carbon atoms) by an organic peracid in the presence of a catalyst.
In oxidizing benzene rings for thereby introducing the hydroxyl group therein, there have already been suggested the following techniques. French Pat. No. 1,479,354, for example, relates to a method for producing pyrocatechol and hydroquinone by the oxidation of phenols. The oxidation is effected by a peracid, with phosphoric acid used as a catalyst in an amount of 1 - 2% by weight based on the phenol. As concerns the treatment following the reaction, since the distillation, if performed in the presence of the acid catalyst, entails degradation of the yield of dihydric phenol, it is necessary that the reaction solution should be neutralized prior to distillation. The yield is as low as 54%. In the oxidation of phenols by peracids, it has already been known that such acid substances as hydrogen fluoride and boric esters besides said phosphoric acid accelerate the oxidation. The addition of such acid substances barely serves to increase the yield to about 65% at most. The addition, at the same time, increases by-products. It is also known to the art that the oxidation of phenyl ethers by peracids leads to formation of monoethers of dihydroxy phenols. It is further known that the oxidation is effected by highly reactive organic peracids and that the presence of boron trifluoride or some other similar catalyst is effective in further heightening the reactivity of said organic peracids. (J. D. McClure, J. Org. Chem., 27, 627 (1962).)
The primary object of this invention is to provide a method for the manufacture of dihydric phenols in unusually high yields by the oxidation of monohydric phenols.
Another object of this invention is to provide a method for the manufacture of dihydric phenols in unusually high yields by the oxidation of phenol ethers.